Electrical signaling



Oct. 20, 1931. H. A. THOMPSQN 1,827,829

ELECTRICAL S IGNALING Filed July 19, 1930 INVENTOR w T33 I H, H. hompson, N ba-m m ALL; ATTORNEY v pf:

Rowan]; A. trnorrrson, or nnenwoon, PENNSYLVANIA, ssIeNoR 'ro 'rir-E' NIoN swrrcn -& sreNaL COMPANY, on swIssvALn, PENNSYLVANIA, n conronArIoNor v TEENNSYLVANIA i Application filedJulyi19,

My invention relates to electricallsignaling apparatus, and particularly to apparatus for indicating the length of a train.

I will describe one form of apparatus e 1nbodying my invention, and will then'point out thenovel features thereof in claims.

The accompanyingdrawing is a diagram-' track sections AC and C---F. Track circuit current is supplied to the rails of each track 'section'from a track transformer, designated by the reference character T-with a suitable exponent, and having its secondary connected across the rails adjacentthe exit end of the corresponding;section-in series with the usual current limiting impedance 19.

' The primary of each transformer T is supplied with alternating current from the terminals X and Y of a suitable source of current not shown in the drawing. Each track section is also provided with a track relay, designated by the reference character R with a suitable exponent, and comprising two windings 3 and l, one of which, 3, is constantly connected across the rails adjacent the entrance end of the corresponding section. The other winding 4 of each track relay is constantly supplied with alternating current from terminals X and Y, so that when track circuit current is supplied to winding 3 of the relay from the rails of'the correspond ing section, the track relay is energized.

An insulated joint 5 is located in rail-P of section A-C ata point B which is a comparatively short distance, for exampleone rail lengh, in rear of the exit end of this section. Twoother insulated joints 5 and 5 are located in rail 1" of section C-F at the points D and E, respectively. The points D.

and E may be spaced from the entrance end of section C-J? any -su1ta ble distances but, for purposes ofexp'lanation I- Wlll assume '1 LECTRICAL sre ALINe v 1936. Serial No. 469,241.

that the point D is spaced from the entrance I end ofsection C-Fa clistancecorresponding' to the length of a'train composed of six cars, while the point E is spaced from, the entrance end ofsection CF a distance which corresponds to the length of'a train composed-of ten cars. i

:Associated with each of the joints'5 is an auxiliary relay, designated by the reference character G with an exponent corresponding to the location. Each relay G is intended to beoperatedin response to the differencein potential existing between the confronting,

ends of rail 1*" at the associated jointj5 when the section in which the jointis included is unoccupied between suchjointand theeXit end of the section. Tothis end, each rela'y,asj 1 here shown, is connected through a full wave; rectifier 8 with the secondary 6 of a transformer, designated by the reference character J with'a suitable distinguishing eXponent, and having its primary 7 connected with" I the rails on opposite sides of-the correspondingjoint' 5.; With this arrangement, it will be plain that the alternating current supplied to the rails of'section AO from track transformer T normally flows through the rails of this section in series and through winding 3 of track relay B and primary? of transformer J Similarly, the alternating current supplied to therails of section CF by track transformer T5 normally flows through the railsof this section in series andthrough the winding 30f track relayR and the primary 7 of each of the transformers J and J The alternating current thus sup-' plied to each transformer energizes the associatedrelay G. y i r The track relay R and the auxiliaryrelays G control three stick relays 1-1 H and H Relay H is provided'witha pick-up circuit which passes from terminal X through back contact 9 of'trackrela "R front contact 10 of auxiliary relay v front-contact 1111 of auxiliary relay G and'winding 9 of relay H to terminal Y, Relay H is also provideol'with a stick circuit"which passes from terminal X through backfcontact 9 Y. Relay H is provided with a pick-up circuit whichpasses from terminal K through back contact 9 of track relay R front contact 10 of relay G back contact 11-11 of relay G front contact 1313'* of relay G and winding of relay H to terminal Y. Relay H is also provided with a stick circuit which passes from terminal X through back contact 9 of track relay R front contact 14: of relay H and winding of relay H to terminal Y. Relay H is provided with a pick-up circuit which passes from termianl X' through back contact 9 of track relay R front contact 10 of auxiliary relay. G back contact l1-11 of auxiliary relay G back contact 1? 13 of'auxiliary relay G and winding ofrelay H to terminal Y. Relay H is also provided with a stick circuit which passes from terminal X through back contact 9 of track relay R, front contact 15 of relay H and winding of relay H to terminal Y. e The relays H H and H in turn, control three indicating devices, here shown as electric lamps, and designated by the reference characters L L and L respectively. These lamps will usually be located at a remote point, as in a signal tower or train despatchers office. 'Lamp L is provided with a circuit which passesfrom terminal Xthrough front contact 16'16 of relay H and the filament of lamp L to terminal Y. Lamp L is provided with a circuit which passes from terminal X through back contact- 16 16 of relay H front contact 1717 of relay H and the filament of lamp L to terminal: Y. The lamp L is provided with a circuit which passes from terminal X through back contact 1616 of relay H back contact 1717 of relay H front con tact 18 of relay H and the filament of lamp L? to terminal Y. H

As shown inthe drawing, section A-C and CF are both unoccupied. The relays G are therefore all energized. Track relay R is also energized. Relays H H and H are therefore all deenergized, and the lamps L? L and L are all extinguished.

In explaining the operation of the apparatus, I will first assume that a train which is moving in the direction of the arrow, and which is shorter than the distance from the point C to the'point D traverses the stretch .of track illustrated in the drawing. Assoon as the front end of the train passes point B, current fromtrack transformer T will be 7 shunted away from the primary 7 of trans-- i become completes the circuit for lamp L and can become energized while any portion of the train occupies portion BC of section AC. When thetrain enterssection CF, currentwillbe shunted away from winding 3v 0f track relay R and track relay R will deenergized, and will, close' its back contact 9; This hasno effect on the re mainder of the apparatus, however, until the rear of the train passes outof section AC,

whereupon relay G picks up and closes its front *contactlO. Sincethe train is shorter than, the distance from the point C to the point D, relay G is energized, so that when relay G? becomes energized, the pick-up circuit for relay H will become closed, and relay H will become-energized; The closing of front contact 16 516 of rel ayl-l completes this lamp therefore becomes lighted to'indicate that the train which has ust entered section CF is shorter than the distance from the point C to the point-D. When the front end of the train passes point D, relay G will become deenergized and will open itsfront con tact 11-11 and closeits back contact 11-11", The opening of front contact 11-11 of relay G interrupts the pick-up circuit for relay H but relay l-l remains energized by virtue of the stick circuit previously traced for this relay which is then closed at front contact 12 of this relay. 1111 of relay G completes the pick-up cir cuit for relay H and relay H becomes energize'd and closesits' stick circuit. This has no effect on the remainder of- .the apparatus under these conditions, however, since the circuits for the lamps L and L? are now both open at back contact 1616 of relay H Likewise, when the front end of the train passes point E, relay G will become deenergized, thereby completing the pick-up circuit for relay H so that this latter relay. will'be- The closing of back contact come energized andwill close its stick circuit.

This also has no effect on the remainder of the apparatus under these conditions, however, 1

due to the circuits for the lamps L and L being open at back contact 1616 of relav H Nhen the train has passed completely out of section CF, current will again be sup- 1 all of the circuits for therelays H H and H.

are interrupted, and these relays therefore become deenergized. Lamp L then becomes extinguished. The apparatus is then restored to its normal condition in which itis illustrated in the drawing.

I will now assume-that atrain which is longer than the distance from the point C to the point D, but which is shorter than the distance from the point C 'toi'the point E traverses, in thedirection of the arrow, the

' ergized. Relay 'H is deenergized under these conditions, since itspick-up' circuit is open at front contact 11-,11 of relay G and lamp Ifitherefore becomeslighted'to indicate that the train-in section 'C.'G is longer than the: distance, fromthe point C to the point D, but is shorter than the distance from the point C to the point E; When the front end of the train passes point- E, relay Gnwill become'deenergized, andwill open its front contact 13 13 and close its back contact 13-13", When front contact 1313 otfrelay G is opened, the pick-up circuit previously traced for relay H is opened at this-contact but relay: H remains energized due to its stick circuit which is now I closed at its front contact 14. WVhen back contact 1313 of relay G is closed, the

r ickup circuit for relay H is closed, and a this relay becomes energized and closesits- 7 a mg sa d third contact in its operated cond1- stick circuit but since the circuit for lamp L is then open at back contact 17--17 of relay H the energization of relayH does not atfect the remainder of the apparatus. Whenthe train has completely passed outof section 6 -5, winding 3 of relay R and relays G and G will all become energized. When winding 3 of relay R becomes energized, it opens its back c'ontact'9, thereby deenergizing relays H and H The lamp L then becomes extinguished and the parts are restored to their normal conditions If a train which is longer than the distance from the point C to the point E traverses the stretch of track illustrated in the;

drawing, then when'the rear'end of thetrain has cleared section AC, winding 3 of track relay R as wellas relays G and G will all be deenergized. 'As a result, when relay G becomes energized and closes its front contactllO under these conditions, the pick-up. circuit for 'relay'H 'will be completed, and relay H will thereforebecome energized and will close its stick circuit. Relays H and H? are then both deenergized, and lamp L therefore becomes lighted-to indicate that, the train is longer than the distance from the point C to the point E. When the train has completely cleared section CF', winding 3 of track relay B and relays G and Gr will again become energized. Relay H will therefore become 'deenergi'zed and will exstored to their normal conditions in which they are illustrated in the drawing." Although I have herein shown and described only-one form of railway-traffic con- I trolling apparatus embodying my invention, it is understood that Various changes and modifications may be made therein withinthe:

scope of the appended claims without departing from the spirit and scope of my invention. i

Having'thus described my invention, what I claim'is:- v-

1. In combination, a first contact, means for operating said first contact when'the front end of a train passes a first point along the'trackway and for subsequently maintain ing said first contact in itsoperated condition until the train has passed beyond a second the t rackway located in advance ofsaidsecond point, a third contact, means for operat-- ing said third contact when the front end of the train passes a fourth point along the trackway located between said second and third points and for subsequently maintaintion until said train has passed beyond said third point a'relay controlled by said first, second, and .third contacts in such manner that said relay becomes'energized when said first contact is in its unoperated condition and said second and third contacts are in tion until thetrain has passed beyond a sec-.

0nd point along the trackway in advance of said first point, 'a 'second contact, means for operating said second contact when 'front end of the train passes said second point and for subsequently maintaining said second contact in its 'operated condition until the train h as passed beyond a third point along the track way located in advance of said second point, a

third contact, means for operating said third contact when the front end of the train passes a fourth point along the trackwaylocated betweensaid second and third points and for subsequently maintaining said third contact in its operated condition until said train has passed beyond said third point; a relay controlledby said first, second, and third contacts in such manner that said relay becomes energized when said first and said third consaid'seco'nd contact is'in-its operated condi-.

tion, and indication means controlled by said relay. H

3. Incombination, a first normally closed contact, means: for opening said first normally'closed contact when the front end of a trainpasses a first point along the track-way and for subsequently holding saidfirst normally. closed contactsopen until the train has passed beyond a second point along the track- .vay locatedin advance of said first point, a

normally open contact means for closing said normally open contact when the front end ofthe train passes said. second point and for subsequently holding said normally open contact closed until the train has'passed'beyond athird point along the traolrway located in advance of said second point, a second V normally'closedrcontact, means for opening between said second and fourth points.

l. Incon bination, a first normally closed contact. means for opening said first normally closed contact when the front end of a train passes a firstzpoint along the trackway and for subsequently holding said first normally closed contact open untilthe train has passedbeyond a second point along the trackway located in advance of'said first point, a-

normally open contact, means for closing said ormally open contact when the front end of the train passes said second point and for subsequently holding said normally open contact closed until the train has passed beyond a -third point along the trackway located in advance of said second point, a second normally closed contact, means for opening said second normally closed contact when the front end. of the train passes a fourth point alongthe trackway located between said sec Y ond and saidthird points and for subsequent-i ly holding said. second normally closed contact open until the train'has passed beyond said thirdgpoint, a relay, a pick-up circuit for said relay including said three contacts, a

3 stick circuit for said rela includin said normally open contact and a front contact of said relay, and indication means controlled by said relay. 1 r V 5. In combination, a first normally closed contact, means'for opening said first normally closed contact when "the frontend of a train passes a first point along the trackway and for subsequently holding said first normally closed contact open until the train s has passed beyond asecond point along the trackway located in advance of said first point,,a first normallyopen'contact, means for closing said first/normally open contact when the front end of the train passes said .7 7

third points and for subsequently holdingsaidsecond normally closed contact open and said second normally 7 open contact closed until thetrainhas passed beyond said thirdpoint, two rela-ys, a pick-up circuit for one of said relays including said first andsecond normally closed contacts and said first normally-open contact, a stick circuit for said onerelay including said first normally open contact and a front contact of said one relay, a pick-upcircuit for the other relay lncluding saidfirst and second normally open contacts as well as said first normally closedcontact, a stick crrcuit for-said other relay'including said first normally open contact and a front contact of said other; relay, and indication neansselectively controlled by said relays.

6. Incombination, a first normally closed contact, means for opening said first normal- 1y closed contact: whenthe front end of a train passes a first point along the trackway and for subsequentlyfholding said first normally closed contact open until the train has passed beyond a second point along the trackway located advance ,ofsaid first'point, a first normally open contact, means for closing said first normally open contact when the front end of the train passes said second point andfor subsequently holding said first normally open contact'closed until the train has passed beyond a thirdpoint, along the trackway located in advance of said. second point, a secondtnormally closed contact and a second: normally open contact, means for opening said second normally closed contact and for closing s'aidsecond normally open contact when the front end of the train passes a fourth point along the trackway located between said second andithird points and for subsequentlyholding said second normally closed contact open'and said second normally open contact closed until the train has passed beyond said third point, a

third normally closed contact and a third normally open contact, means for opening said third normally-closed contact and for closing said third normally open contact when the front end of the train passes a fifth point along the trackway located between said fourth and said third points and for closedcontact open and said thirdnormally open contact closed untilithe trainhas passed beyond said third point, three relays; a pickup circuit for a first one of saidrelays including said first normally open contact, saidfirst normally closed contact, andsaid second nor- 'mally closed contact; a stick circuit -for'said third one of said relays includingsaid first contact, and saidthird" normally open con first relay includingsai'd first normally open contact and a front'contact of said first relay;

a' pick-up circuit for" a second one of' said relays including said first normally open contact, said first normally closedcontact, said second normally open contact'and said third normally closed contact; a stickcircuitforc said second relay including'saidfirst normally open contact and a front contact of said second-relay; a pick-up circuit for a normally open contact, s'aidfirst normally closed contact, said secondinormally open tact; a stick circuitfor said third relay including said first normally open contact and K a front contact of said third relay; a first indicating device controlled byv a front contact of said first relay,;;a second indicating device controlledby a back contact of said first relay and'a front contact of said second relay, and a third indicating device controlled: by aback contact ofsaid first relay and a back contactof'said second relay as well as a front COIltHQOtOff said third relay.

7..In combination,a first normally 'clo'sed contact, means for opening said first normally closed contact when the'frontend of a train PQSSBSDQ, first'vpoint'along'thetrack- Way and forsubsequently holding said first normally closed contact 'open until the-train has passed beyond a'secondpoint al'ongthe trackway located in advanceof said first point, a first normallyopen'contact, means for closing said first normally open contact when the front end of the train passes said secondpoint and forsubsequentlyholding said first normally open contact closed until the trainhas passed beyonda third point along the trackway located in advance of said 7 second point,a second normally closed contact and a second-normally open contact, means for opening said second normally closed contact and for closing said second normally o-pen contact when the front end of the train passes la fourthlpoint along the trackway located between said second and third" points and for s subsequently holding said second normally closed contact open: and said secondnormally V open'contact closed until the train has passed "beyond said'thi'rd point ,;athird; normally I closed contactand as third normallyopen 'contacu'meansfor opening saidthird nor mally closed' contact and for closing said thirdnormally open contact'when the front end.- of the train passes a; fifth point along point, three relays; a-pick up circuit for a first one of saidirelays including said first V normally open contact, said first normally closed-contact; a stick circuit for'saidfirst relay.including said first normally opencon- Jtact and a front contact of said first relay; a pick-up circuit for a second oneof'said relays including said first normally open contact,

"cuit'for said third relay including said first train has passed beyond saidthird point,

the trackway located between said fourth and said'third points and for'subsequently holding said thirdflnormally closed contact open and said third normally open-contact closed until the train has passed beyond said third closed contact, and said second normally said firstnormallyclosed contact, saidsecond normally open contact-and-said' third-non mally' olosed'c'ontact; a stick circuit for said "secondrelayincluding said first normally normally. open contact anda front contact of said third relay, and indicatiOn me'a n's selectively controlled by said three relays."

8. lna-combinatiom four normally energized relays, meansfordeenergizing a first one ofsaid relays when thefront end of a train passes a first predetermined point along 'the'trackw'ay and for subsequently maintain:- ing said first relay in its deenergized'condition until the train has passed beyonda second point along the trackwaylocate'd in advance of said first-point, means for deenergizing a second one of said relays whenthe front end of: thetrainpasses said secondpoint and for subsequently maintainingsaid second'rela-y in its deenergized condition until the-train has passed beyond a third point along the trackway located in advance'of said'second point, means for deenergizing a third on'e of said relays when the front end of the train passes a fourth point-along the'trackway located between said second and third points and for subsequently maintaining said third relay in its deenergized condition untilthe means for deenergizing afourth one of said relayswhen the front endof'the train passes a fifth point along the tracliway locatedbetween said fourth and said third points and I for subsequently maintaining said fourth relay in its deenergized condition until the train has passed beyond saidthird point; a fifth, a sixth, and aseventh relay; means for energizing said fifth relay when said first-and; third relays are both energized and said sec} 0nd relay is deeri'ergized, ineansfor ener' gizing said sixth relaywhen said first and said fourth relays are energized and said second and third relays are deenergized; means for energlzing said seventh relaywhen gized relays, means for deenergizinga first one of said-relays when the front end of atrainpasses a predetermined point along the trackw'ay andfor subsequently maintaining said first relay in its deenergized condition until the train has passed beyond a second point along the trackway located in advance of'said first point, means for deenergizing a-second one of saidrelays when thefront end of the train passes said second until the train'has passed beyond a third point along the trackway located in'advance ofsaid second point, means for deenerg zlng a third one ofsaid relays when the front end of thetrain passes a fourth point alongthe trackway located between said second and third points and for subsequently maintaining said third relay in its deenergized condition, until the train has passed beyond said third point, means for deenergizing a fourth ne ofsaid relays when the front end of the train passes a fifthvpoint along the trackway located between said fourthgand said third "points and for subsequently maintaining said fourth relay in 1ts deenerglzed condi-v tion until the train has passed beyondsaid' .relay; a stick circuit for said sixth relay including said back contact of said second relay and a front contact of said sixth relay; a

pick-up circuit for said seventh relay includmg said back contact of said second relay,

said front contact of said first relay, said back contact of said third relay, and a back contactof said fourth relay; a stick circuit for said seventh relay including said back contact of said second relay and a frontcontact of said seventh relay; three indicating devices, a circuit for afirst oneof said devices. including a front contact ofsaidfifth relay; a circuit for aseco-nd one .ofsaid devices including a back contact of said fifth relay and a front contact of said sixth relay;

"and a circuit for the remaining one of said indicating devices including said back contact of saidfifthrelay, a back contact of said sixth relay, and a' front contact of said seventh relay. y Y

10. Incombination,-a section of ra lway track, a source, of energy connected across the rails adjacent the exit end of-the section, a

track relay connected acrossthe rails adjacent the entrance end of the section, two 1nsulated oints in one rail located at spaced points intermediate the ends of such section,

twowindings one connected'across each of said joints, and means controlled by said track relay and by said two'windingsand effective when and only when a train has completely entered said section for indlcating the length of said train. point and for subsequently maintaining sa d second relay in its deenergxizedi' cond tion 11. In combination, a section of railway track, a source of energy connected across the rails adjacent the exit end "of the section, atrack relay connected across the rails adjacent the entrance end ofthe section, a

diate the ends ofthe section, in advance of said first joint, two windings one connected across each of said lnsulated joints, acontact, means for operating said contact-When the front endof artrain passes a point along "the trackway in rear ofthe entrance end of said section and for subsequently, maintains ing said contact in." its operat'edcondition until thertrain has completelyentered said section; and means controlled jointly bysaid contact, sald two windings, and said relay for indicating whethera train occupying.

said section is shorter than the distance from the entrance end of said section to said first joint, or is longer than the distance from the entrance end of said first; section to said first joint but shorter than the distance fromthe v jacent the'entrance end of'the section, an

insulated joint in one rail of said section 1'0- cated in advance of the entrance-end of the section, a transformer having its primary connected across said joint, a' second relay at times receiving energy from said transformer, a contact, means for operating said contact when the front end of a train passes a point, along the trackway in rear of the entrance endvof said sectionan'd for subsequently maintaining said contact'in its oper ated condition Vuntilthe train ha's'completely entered said section, a thirdrelay; means-for energizingsaid third relay When'saidtrack relay is deenergized, said i-sec o'nd relay; is

energized, and said contact -isi in itsunoper- 1 ated condition; and an indicatingdevice controlled by said third relay.

13. In combination, a section of railway track, a source of energy connected across the rails adjacent the exit end of the'section, a track relay connected across the rails adj aeent the entrance end of the section, an insulated joint in one rail of said section located in advance of the entrance end of the section. a transformer having its primary connected across said oint, a second relay at times receiving energy from said transformer,

is in its unoperated condition, and indicat-V ing devices selectively controlled by said third and fourth relays.

14. In combination, a section of railway track, a source of energy connected across the rails adjacent the exit end of the section, a track relay connected across the rails ad j acent the entrance end of the section, a first insulated joint in one rail of the section in advance of the entrance end of the section,

a second insulated joint in said one rail of the section in advance of said first joint,"a

first transformer having its primary connected across said first insulated oint, a second transformer having its primary connected across said second insulated joint, a second relay at times receiving energy from said first transformer, a third relay at times receiving energy from said second transformer, a normally closed contact, means for opening said contact when the front end of a train passes a point along the trackway in rear of the entrance end of said section and for subsequently holding said contact open until. the train has completely entered said section, a fourth, a fifth, and a sixth relay; a pick-up circuit for said fourth relay including a back contact of said track relay,

said normally closed contact, and a front contact of said second relay; a stick circuit for said fourth relay including said back contact of said track relay and a front contact of said fourthrelay; a pickup circuit for said fifth relay including said back contact of said track relay, said normally closed contact. a back contact of said secondrelay, and a front contact of said third relay; a stick circuit for said fifth relay including said back contact of said track, relay and-a front contact of said fifth relay; a pick-up circuit; for said sixth relay' including"said back contact of said track relay, said normally closed contact, said back contact of said second relay, and'a back contact ofsaid third eluding said' back contact of" said triack relay. and a front contact of said 'sixthrelay;

and in dication means selectively controlled by said fourtlnfifth, and sixth'relays. 7

I 15. In combination, twoi adjacentse'ctions of railway :track, two source's of energyv'one connected across the rails adjacent the exit end of each section, a firstins' ulated j oirit in one rail located intermediate the endsof tlie forward- -one of said sections, a second=ine sulated joint in one'ra'il locatedintermediate the endslof the rear one of said sections, two windings one connected across each" said joint, andmeans controlled partly by both: "said'windings for indicating whetherfa'train occupying said forwards ection is longer or shorter'th'an the distance'from theentrance' end of the forward section to said 'first' insulated oint.

connected across the railsadjacent the exit end'of each section, a-track relay connected acrOSsthe rails adj acentlthe entranceen'd of the forward one of s' aid sections, a first insulated joint in one rail located intermediate the ends of said'fo'rward section,a secondin relay; a stick circuitforsaid sixth relay'in- 16. In combination, two adjacent seetions of railway tracln'twosources of energyonef 'sulated j ointin one rail located'intermediate the endsof therear-one of said sect-ions, two

windings one'connected across-each said joint, and means jcontrolle'd'by both-said windings and by said, track relay for indicating whethera train occupying said forward's'ec-I tion is longer orishorterthanthe distance from the entrance end of said forwardseetion 'to'said first insulated joint connected across the rails" adjacent the. exit en of each section, a track relay connected across therailsfadjacentthe entraneeend of the forward one of said sections, a first insulatedjoint in one rail located intermediate the ends of said forward section, a second insulated joint in one rail located inter1nediate the ends of the'rear one of said sections, a first transformer havlng its primary con- 7 nected across said first insulated joint, a secins;

1 7.' I n-combination, two adjacent sections of -rallwayftrack, two sources of energy one 1 0nd relay receiving energy from said first transformer, a second transformer having its primary connected across said second 1n-- sulated joint, a third relay receiving energy from said second transformer, and means controlled by said track relay and by said second and third relays, .for indicating whether a train occupying said forward sec-Y fromthe entrance end of said forwardusect on to sald first insulated jointk 18. In combination, two adjacent sections tion is longer" or shorter than the distance of railway track, two sources of energy one Connected across the rails adjacent the "exit end of each section, a track relay connected across the rails adjacent the entrance end of the forward one of said sections, a first insulated joint in one rail located intermediate the ends of said forward section, a second insulated joint in one rail located intermediate the ends of the rear one of said sections, a first transformer having its primary connected across sa d first insulated oint, a first rectlfier, a second relay connected with the secondary of said first transformer through said first'rectifier, a second transformer having its primary connected across said second insulated joint, asecond rectifier, a third relay connected Withthe secondaryof said second transformer through said second rectifier, and means controlled by said track relay and by said secondand third relays, for indicating whether a trainoccupying said forward sectionis longer or shorter than the distance from the entrance end of said forward section to said first insulated joint.

19.v In combination, a section of railway track, a source of energy connected across the rails ad acent one end of sa1d sect1on,'a V

track relay connected across the rails adjacent the other end of said section, an insulated 1 joint in one rail of said section, a winding connected acrosssaid jolnt, and means controlled by said track relay and by said winding' for indicating the length of a train entering sa1d section. i

20. In combination, a section of railway track, a source of energy connected across 7 the rails adjacent one end of said section, a

track relay connectedacross the rails adjacenttheoth-er end of said 'sectionyan insulated o nt mone'rall of sa1d sectlon, a, windingconnected across sa1d oint, a stlck relay controlled by said track relay and by said winding, and means controlled by said stick relay for indicating the length of a train entering said section.

In'testimony whereof I afiiX my signature.

QHOWARD A, THOMPSON,

moo 

